The present invention relates in general to sensor heads for measuring machines and in particular to such a sensor head in which, for one coordinate at least, a straight line guiding mechanism is provided which comprises a first base part and a second base part displaceable relative to the first base part in both directions of the coordinate with spring means acting in this coordinate being provided which brings the two base parts into abutment.
A simiar arrangement is described in German patent No. 11 36 555. There, by means of an extension spring, a movable plate of a spring parallogram is pulled against a stop provided on a fixed plate of the spring parallelogram. No stop is provided for the opposite direction of movement.
In German As No. 23 56 030 a sensor for workpiece probing is described, having one spring parallelogram per coodinate. Two spring loaded stop studs are mounted on a fixed base part. In the position of rest between these stop studs, balls mounted in a spring housing attached to the fixed base part, as well as a bending beam attached to the movable base part, are wedged between these stop studs. Since the stop balls as well as the bending beam apply against the same abutment area or areas, slack may result if, for example, the stop faces of the stop studs are not exactly parallel or the diameters of the stop balls and of a head ball of the bending rod differ. The means for eliminating such slack are expensive.
In German As No. 23 56 030 the bending rod has a steep force distance characteristic. The spiral springs for the balls have a flat force distance characteristic. The bending rod is to be deformed before the respective compression spring during workpiece probing.